Process for transporting thermal energy

ABSTRACT

Process for transporting thermal energy from the place where it is produced to the place where it is required for use by catalytic reforming of methane or natural gas, transporting the thus obtained gas mixture after cooling through pipe lines to the place where the energy is required for use, catalytically methanizing the gas mixture into methane and utilizing the heat liberated during this reaction in the manner required.

United States Patent Hilberath et al. [4 1 Sept. 12, 1972 PROCESS FORTRANSPORTING [56] References Cited THERMAL ENERGY UNITED STATES PATENTS[72] Inventors: Friedrich Hilberath, Hans Teggers,

both of D 5047 wesseling near 3,558,047 1/1971 Wolfgang et al ..237/12Cologne, Germany Primary Examiner-Edward J. Michael [73 Assignee: UnionReinische Braunkohlen Kraft- A ynn lly & Hull stoff Aktiengesellschaft,Wesseling near Cologne, Germany ABSTRACT [22] Filed; Dem 27 1968 Processfor transporting thermal energy from the place where it is produced tothe place where it is PP N08 787,334 required for use by catalyticreforming of methane or natural gas, transporting the thus obtained gasmixture [30] Foreign Application P i i Data after cooling through pipelines to the place where the energy is required for use, catalyticallymethanizing Jan. 16, 1968 Germany ..P 16 92 253.5 the gas mixture intomethane and utilizing the heat liberated during this reaction in themanner required. [52] US. Cl. ..237/8l, 48/197, 176/39,

176/92 6 Claims, 1 Drawing Figure [51] Int. Cl ..F24d 7/00 [58] Field ofSearch ..l65/l;237/l, 81

, l I He'af Hep! A .B I a l l l l l PA'TENTEDSEP 12 I972 Hep! IINVENTORS Friedrich Hi lberaflu PROCESS FOR TRANSPORTING THERMAL ENERGYFIELD OF INVENTION This invention relates to a process for transportingthermal energy.

DESCRIPTION OF PRIOR ART Various methods have been adopted fortransporting thermal energy from places where it is generated in anyform to where it is required for use. In spatially restricted areas, forexample in towns or industrial complexes, thermal energy may be directlytransported by piping heated liquid, for example water, diphenyl, orsteam, through pipe lines to the site where the heat is required foruse. This system inevitably involves losses 7 of energy, for examplethrough the dissipation of heat to the area surrounding the pipe lines.Accordingly, the direct transportation of heat by this system is limitedto short distances. In addition this transport system can individualprocess stages.

SUMMARY OF INVENTION It has now been found that heat-can be transportedwith advantage from the site where it is generated to the site where itis required for use, by using the heat generated for the catalyticreforming of methane, transporting the resulting gas after it has beencooled through pipe lines to the site where-the energy is required foruse, catalytically methanizing the gas and exploiting the heat therebyliberated in the manner required. It is thus possible to utilize thethermal energy as such at the place where it is required.

DETAILED DESCRIPTION'OF INVENTION The methane used may be recycled tothe reforming plant, although it may of course also be used for anotherpurpose, for example in chemical reactions or optionally for example inpartial combustion.

The process of the present invention may be applied with particularadvantage when high temperature heat has to be carried over considerabledistances. Heat of this kind is generated, for example, in nuclearreactors. It may also be produced, for example, through the combustionof inexpensive fuels. Natural heat sources may also be used. Instead ofpure methane, is is also possible to use gases containing methane, suchas natural gas. The concentration of inert constituents, or otherhydrocarbons, or other compounds should not be too high if the methaneis to be recycled, in order to prevent excessively high losses throughdilution or through secondary reactions.

The methane may be reformed and the gases thus obtained may bemethanized by any process known per se. One standard process for exampleis steam reforming, using nickel catalysts at about 700 C, and can becarried out at atmospheric pressure or at elevated pressure. Knownmethanization processes operate, for example, with nickel or noble metalcatalysts. When these processes known per se are used, precautions mustof course be taken to ensure the absence of harmful compounds in thegases.

The process according to the invention enables thermal energy to becarried with advantage over long distances and to be re-used as such. Itis of advantage that more than percent of the thermal energy which isreleased or used in the reforming of methane can be recovered at theplace where the methanization reaction is carried out. Any heat energylosses that occur are attributable solely to radiation losses in thereforming plant and the methanization plant, and to the incompletenessof heat exchange between the incoming and outgoing gases.

The process is described in the following, with reference to theaccompanying drawing which is a schematic representation of the process,but the invention is not restricted to the particular arrangement shownor to the Example. No attempt will be made to describe in detail any ofthe process stages which are known per se, such as heat exchange orcooling.

Referring now to the Drawing, the complex A comprises an installationfor releasing heatfrom the helium circuit of a nuclear reactor and amethane steamreforming plant is energized by this heat. Methane isintroduced through pipe 1 into this plant. The methane is converted gasmixture consisting of hydrogen, carbon monoxide and carbon dioxide inaccordance with the reactions CH H 0 C0 3H and CH4 CO2 4H2.

Only a small portion of the methane is left unreacted, depending on theequilibrium of the pressure and temperature conditions selected. It isof particular advantage that no harmful secondary products are formed,which for example could poison the catalyst through deposits or arewithheld from the reaction. The stoichiometric ratios between thecomponents hydrogen, carbon monoxide and carbon dioxide remain intact asthey do in the inverse reaction of such an equilibrium. The gas mixtureobtained in the reforming plant is conducted to the site where thethermal energy is to be used through pipe 2, to complex B. At complex B,which comprises the installations for methanizing the reforming gas andfor utilizing the heat obtained during this exothermic reaction, thecomponents carbon monoxide and carbon dioxide are converted back intomethane. The methane is recycled to the reforming plant through pipe 1.If the methane obtained in B is used for chemical reactions, forexample, a corresponding quantity of methane is added to the circuitthrough pipe 3. Depending upon the course of the reaction, from 42 to 50kcal. of heat can be brought to B per mol of methane reformed. In otherwords, large quantities of heat can be carried from A to B given acorresponding methane through-put. Since the reaction system proposedhere is carried out in a closed circuit, the losses of gas componentsare small. They only comprise leaks and the dissolved gases in the waterof reaction which is removed after the methanization stage in complex B.

The catalysts commonly used for the reforming and methanizationreactions have a long service life and are resistant to abrasion.Reforming may also be carried out, for example, in the presence ofcarbon dioxide.

EXAMPLE In this particular instance, the heat to be transported comesfrom a helium gas circulating in a high temperature reactor at aboutl,000 C. The heat is removed from the helium circuit by causing the hothelium to flow directly around the catalyst-filled pipes of the methanereforming plant. Reforming was carried out in the usual way by adding 3mols of steam per mol of methane, at about 900 C. and 55 atms. Aftercondensing out the excess steam, followed by cooling, the resulting gaswas delivered through a pipe line, compressed to about 70 atms.pressure, to the methanization site, i.e., where the heat is requiredfor use. Methanization of the reforming gas was carried out in the usualway at about 300 C. over one of the conventional methanizationcatalysts. The resulting methane was recycled through another pipe tothe methane reforming plant. In the case of a transport of 1 million Nm/h of methane through a pipe line of a length of km, the cost per unitof heat at the consumption site amounts to only about 65 percent of thecosts which would be involved if the heat were to be converted in asteam power plant and transported in the usual way in form of electricalcurrent.

What is claimed is:

l. A process for delivering thermal energy a geographical distance froma supply of such energy, which process comprises using the suppliedenergy to reform methane with water and thus produce a gaseous mixtureof hydrogen and oxides of carbon, transporting such gaseous mixture tothe delivery location, and methanizing the mixture at that location togenerate thermal energy and regenerate the methane.

2. The process of claim 1 in which the methane reformed is in a streamof natural gas.

3. The process of claim 1 in which at least some of the regeneratedmethane is recycled back to the energy supply.

4. The process of claim 1 in which the energy supply is a nuclearreactor.

5. The process of claim 1 in which the energy supply is a fuel burner.

6. The process of claim 1 in which the transporting of the gaseousmixture to the delivery location is effected with such mixture undersuperatmospheric pressure.

2. The process of claim 1 in which the methane reformed is in a stream of natural gas.
 3. The process of claim 1 in which at least some of the regenerated methane is recycled back to the energy supply.
 4. The process of claim 1 in which the energy supply is a nuclear reactor.
 5. The process of claim 1 in which the energy supply is a fuel burner.
 6. The process of claim 1 in which the transporting of the gaseous mixture to the delivery location is effected with such mixture under superatmospheric pressure. 